In cellular communication systems, antenna installations are provided at separated locations to enable communication with mobile system users within a surrounding cell area. As cellular use and installations increase it has become apparent that cost savings or improved performance, or both, could be provided through availability of improved antennas and antenna systems. A common type of cell antenna installation utilizes three 120 degree single beam sector antennas, to provide 360 degree azimuth coverage. Antenna systems suitable for providing coverage of a 120 degree sector with improvements in antenna gain, coverage area and other operational aspects are described in copending U.S. patent application Ser. No. 08/379,820, titled "High Gain Antenna Systems for Cellular Use", filed Jan. 27, 1995, and assigned to the same assignee as the present invention. The systems described therein include provision for use of multiple beam antennas for providing coverage of each such 120 degree sector of a cell.
However, many cell antenna installations rely on antennas mounted on towers or poles in order to achieve desired coverage. Such towers and poles are typically designed and constructed with finite limits on safe levels of loading under high wind conditions, in order to avoid structural failure. Use of a multi-beam antenna in such installations may typically necessitate an antenna having a larger size, as compared to a single beam 120 degree sector antenna designed for the same frequency band of operation. As a result, the objective and benefits of employing multi-beam antennas in such tower installations may not be achievable where high wind loading of a larger antenna would potentially exceed the applicable wind load limit.
It is therefore an object of the present invention to provide antennas having one or more of the following characteristics:
--low wind loading by use of thin cylindrical radiating and reflector units; PA1 --multi-beam or higher gain capabilities, or both, with low wind loading; PA1 --improved radiator construction using a simple microstrip substrate enclosed in a dielectric tube; PA1 --improved tuned reflector construction using thin aluminum rod sections in a dielectric tube; PA1 --beam forming network dual phase coupling to upper and lower radiators; PA1 --low component count of accurately reproducible electrical components for performance and cost benefits; and PA1 --improved operating capabilities for cellular and other applications.